Method for making a battery assembly

ABSTRACT

A terminal for a battery assembly is adapted to lose electrical conduct with a battery cell in the presence of gases within a battery chamber thereby disabling the battery. The disabling of the battery assembly gives the user an indication that the battery is defective and should not be recharged. Additionally, because the battery is disabled, no more gases will be formed in the battery assembly so the seal or the protective envelope will not burst exposing the battery cell to the environment.

BACKGROUND OF THE INVENTION

This invention relates in general to the field of battery packaging.Solid-state batteries are advantageous, since they possess a number ofvery desirable characteristics, including the absence of liquid leakageor gassing, long shelf life, and operation over a wide temperaturerange. A number of solid-state batteries have been proposed.

One such battery which has received wide attention is one employing apolymer cathode, a polymer electrolyte, and a lithium anode. For anexample of a lithium anode battery, see U.S. Pat. No. 4,997,732 issuedto Austin et al. ("Austin et al.").

Lithium is highly reactive, so the lithium battery cell must be sealedin a protective material to exclude air, water and other gases fromcontacting the lithium. The prior art battery cell of Austin et al.shown in FIG. 1 comprises a battery assembly 102, including a thinlaminar battery cell 104 shown in phantom, enclosed by a multi-layeredprotective sheet material 106. Connected to the battery cell 104 areterminals 108 and 110. The multi-layered protective sheet material 106is made of an inner thermoplastic layer, a middle metal foil layer andan outer thermoplastic layer.

A problem with the prior art battery assembly is that a defectivelithium battery cell may form gases that could threaten to burst theseal or the protective sheet material 106 and expose the reactivelithium to the external environment. It is therefore desirable toprovide an improved battery assembly in which this problem is notpresent.

SUMMARY OF THE INVENTION

By using an interconnection scheme where a terminal is adapted to bedisconnected from its contact with a battery cell in the presence ofgases within a protective envelope thereby disabling the battery, it ispossible to give an indication to the user that the battery is defectiveand should not be recharged. Additionally, because the battery isdisabled, no more gases will be formed by the defective battery cell sothe seal or the protective material will not burst exposing the batterycell to the environment.

One aspect of the invention is directed toward a battery assemblycomprising a laminar battery cell, at least one terminal having aportion in electrical contact with the cell, and a protective envelope.The protective envelope defines a chamber therein enveloping the cell toprotect the cell from the environment. At least a portion of theprotective envelope is adapted to flex outward in response to thepresence of gases in the chamber, causing the portion of the at leastone terminal to lose electrical contact with the battery cell.

Another aspect of the invention is directed toward a method for making abattery assembly. The method comprises providing a laminar battery celland a protective envelope with a terminal not in electrical contact withthe cell, enclosing the laminar battery cell in said protectiveenvelope, said envelope defining a chamber, and evacuating and sealingsaid chamber causing the terminal to contact the battery cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a prior art battery assembly.

FIG. 2(a) is a cross-sectional view of a battery assembly of thepreferred embodiment of the present invention showing two terminals incontact with the laminar battery cell.

FIG. 2(b) is a cross-sectional view of the battery assembly of thepreferred embodiment of FIG. 2(a) showing two terminals that have lostcontact with the laminar battery cell due to the presence of gases inthe battery chamber.

FIG. 2(c) is a top view of FIG. 2(a).

FIG. 3(a) is a cross-sectional view of the battery assembly of analternative embodiment of the present invention showing a terminal thathas lost contact with the laminar battery cell due to the presence ofgases in the battery chamber.

FIG. 3(b) is a cross-sectional view of the battery assembly of theembodiment of FIG. 3(a) showing the terminal in contact with the laminarbattery cell.

FIG. 3(c) is a top view of the embodiment of FIG. 3(a).

FIG. 4(a) is a cross-sectional view of the battery assembly of anotheralternative embodiment of the present invention showing a terminalconnected to a check valve that has lost contact with the laminarbattery cell due to the presence of gases in the battery chamber.

FIG. 4(b) is a cross-sectional view of the battery assembly of theembodiment of FIG. 4(a) showing the terminal connected through aconductive portion of the check valve to the laminar battery cell 4.

FIG. 4(c) is a cross-sectional view of the check valve used in theembodiment of FIG. 4(a).

FIG. 4(d) is a side view of a plug used in the check valve of theembodiment of FIG. 4(a).

FIG. 4(e) is a cross-sectional view of the battery assembly of theembodiment of FIG. 4(a) and a vacuum chamber used to evacuate thebattery chamber.

FIG. 4(f) is a cross-sectional view of the battery assembly of theembodiment of FIG. 4(a) and a vacuum hose used to evacuate the batterychamber.

FIG. 5 is a cross-sectional view of the battery assembly of yet anotheralternative embodiment of the present invention showing a terminal ofwhich a portion is contained within the battery chamber.

Equivalent structures are labelled with the same numbers between thefigures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 2(a) is a cross-sectional view of the battery assembly 2 of thepreferred embodiment of the present invention showing two terminals 12and 14 in contact with the laminar battery cell 4. The laminar batterycell 4 includes current collector 4a, cathode 4b, electrolyte 4c, andlithium anode 4d. The laminar battery cell 4 is placed in a protectiveenvelope 6. The protective envelope 6 is comprised of two pieces ofmulti-layer package material 8 and 10. Each piece of multi-layer packagematerial is constructed of at least an outer insulator layer 8a and 10a,a middle electrically conductive layer 8b and 10b, and an innerinsulator layer 8c and 10c.

The multi-layer packaging material can include more than three layers.The multi-layer packaging material 8 and 10 may be one of thecommercially available multi-layered high barrier flexible packagingmaterials disclosed in Austin et al. Another high barrier flexiblemulti-layer packaging material suitable for use as the multi-layeredpackaging material 8 and 10 is a seven layered packaging materialcomprised of (going from the outer layers inward) sixty gauge biaxoriented nylon (BON)/fifteen pounds of polyethylene (PE)/0.0003foil/seven pounds of PE/sixty gauge BON/seven pounds of PE/four mils ofSurlyn® brand resin from Dupont. For this seven-layered packagingmaterial, the outer insulator layers 8a and 10a each comprises a layerof sixty gauge BON, and a layer of fifteen pounds of PE; the middleelectrically conductive layers 8b and 10b each comprises a layer of0.0003 foil; and the inner insulator layers 8c and 10c each comprises alayer of seven pounds of PE, a layer of sixty gauge BON, another layerof seven pounds of PE and a layer of four mils of Surlyn® brand resinfrom Dupont.

Terminals 12 and 14 can be formed by stripping away the insulator layers8a, 8c, 10a, and 10c from areas on the multi-level packaging material 8and 10. The exposed areas of the conductive layers 8b and 10b act as theterminals 12 and 14 so that the terminals 12 and 14 are integral withand form a part of the protective envelope 6.

The laminar battery cell 4 is enclosed in the protective envelope 6. Theprotective envelope 6 forms a battery chamber 16. The battery chamber 16is evacuated and the envelope 6 is sealed in a vacuum sealing operation.The protective envelope 6 now protects the laminar battery cell 4 fromthe environment. Air, water, and other gases are excluded fromcontacting the reactive lithium anode 4d.

The vacuum sealing operation also causes the terminal 12 to flex andcontact the current collector 4a and causes the terminal 14 to flex andcontact the lithium anode 4d. Since air is removed from battery chamber16 in the vacuum sealing operation, the terminals 12 and 14 are flexedinward by the atmospheric pressure. Both terminals 12 and 14 are now inelectrical contact with the laminar battery cell 4. The inner insulatorlayers 8c and 10c prevent the terminals 12 and 14 from shortingtogether.

FIG. 2(b) is a cross-sectional view of the battery assembly of thepreferred embodiment of FIG. 2(a) showing two terminals 12 and 14 thathave lost contact with the laminar battery cell 4 due to the presence ofgases in the battery chamber 16. Terminals 12 and 14, integral parts ofprotective envelope 6, are adapted to flex outward in response to thepresence of gases in the battery chamber 16. Gases produced by adefective battery cell increase the gas pressure in the battery chamber16 thus causing the terminals 12 and 14 to flex away from the batterycell 4. Terminal 12 loses electrical contact with the current collector4a and terminal 14 loses contact with the lithium anode 4d. In this way,the battery assembly 2 is disabled and the user is given an indicationthat the battery is defective and should not be recharged. Furthermore,the recharging of the battery is prevented since terminals 12 and 14 arenot connected to the battery cell. Additionally, since the battery isdisabled, no more gases are produced by the defective battery cell sothe protective envelope 6 will not burst exposing the reactive lithiumanode 4d to the environment.

FIG. 2(c) is a top view of the preferred embodiment of FIG. 2(a) showingthe protective envelope 6 and one of the terminals 12.

A terminal on the protective envelope may also be formed with anelectrically conductive layer surrounding a hole in a packaging materiallayer. FIG. 3(a) is a cross-sectional view of the battery assembly 20 ofan alternative embodiment of the present invention showing a terminal 22that has lost contact with the laminar battery cell 4 due to thepresence of gases in the battery chamber 16. A layer of packagingmaterial 24 can comprise a multi-layer high barrier flexible packagingmaterial with or without a foil layer. If the packaging material 24comprises a multi-layer high barrier flexible packaging material withouta foil layer, the whole packaging material layer 24 comprises aninsulator layer. The multi-layer high barrier flexible packagingmaterial without a foil layer may comprise layers of EZOH, nylon,polypropylene or polyethylene laminated together. Alternately, themulti-layer high barrier flexible packaging material without a foillayer may comprise a PVC coated material such as a PVC coated nylon.

If the packaging material 24 comprises a multi-layer high barrierflexible packaging material with a foil layer, the packaging material 24may comprise the seven-layer packaging material described above or oneof the high barrier multi-layered packaging materials described inAustin et al. Each of these multi-layer high barrier flexible packagingmaterial with a foil layer has an outer insulator layer (not shown).

A section is cut out of a packaging material layer 24 to form a hole 30.The terminal 22 constructed of an electrically conductive layer isattached with adhesive 26 to the packaging material 24 in a manner thatthe hole 30 is sealed. The adhesive 26 may be Surlyn® brand resin fromDupont. The protective envelope 34 is formed from packaging materiallayers 24 and 32 and the terminal 22. The packaging material layer 24 orthe terminal 22 is adapted to flex outward from the battery cell 4 inthe presence of gases formed by a defective battery cell.

FIG. 3(b) is a cross-sectional view of the battery assembly 20 of anembodiment of FIG. 3(a) showing the terminal 22 in contact with thelaminar battery cell 4. As described above in the description of thepreferred embodiment, the protective envelope 34 is vacuum sealed toform the electrical contact between the terminal 22 and the currentcollector 4a. Since only one terminal need to lose contact with thebattery cell 4 for the battery assembly 20 to be disabled, the otherterminal 36 can be permanently attached to the lithium anode 4d. Sincethe packaging material layer 24 comprises an insulator layer or includesan outer insulator layer (not shown), the terminal 22 is not shorted tothe other terminal 36.

FIG. 3(c) is a top view of the embodiment of FIG. 3(a). The hole 30 inthe packaging material layer 24 is shown in phantom. As shown, theterminal 22 may include a tab 22a.

FIG. 4(c) is a cross-sectional view of a check valve 42 used in theembodiment of FIG. 4(a). The one-way check valve 42 is a modification ofa commercially available check valve, such as the check valve availablefrom Robert Bosch Corporation, 15 Seely Ave., Piscapaway, N.J. 08854.The valve 42 is used to allow gases in the battery chamber to escape.

A spring 42f biases a plug 42c so that an inlet 42b of the check valve42 is normally plugged up and fluids from the environment cannot enter.Gas pressure inside the battery assembly, however, may move the plug 42cand allow fluids from inside the battery assembly to exit to theenvironment though inlet 42b.

Additionally, the check valve 42 is modified so that it includes anelectrically conductive portion that is normally in electrical contactwith the battery cell. A terminal 54 is shown in electrical contact withthe battery cell 4 through the electrically conductive portion of thecheck valve 42. The electrically conductive portion of the check valve42 includes a center section 44 of the plug 42c, a wire 42g or a spring42f, and a metal case 42a. The electrically conductive terminal 54 isattached to the metal case 42a of the check valve 42. The metal case 42ais in electrical contact with a spring 42f made of an electricallyconductive material. The spring 42f made of an electrically conductivematerial is in electrical contact with the electrically conductivecenter 44 of plug 42c. Alternatively, if the spring 42f is not made ofan electrically conductive material, an electrically conductive wire 42gmay connect between the electrically conductive center 44 of the plug42c and the metal case 42a. The plug 42c comprises an electricallyconductive center section 44 and an outer rubber seal section 46. Theelectrically conductive center section 44 of plug 42c is normally incontact with the current collector 4a.

FIG. 4(d) is a side view of the plug 42c used in the check valve of theembodiment of FIG. 4(a). This view shows the outer rubber seal section46 and the electrically conductive center section 44.

Looking again at FIG. 4(c), in order to incorporate valve 42 into theprotective envelope, a hole 52 is formed in the packaging material layer50 which is part of the multi-layer package shown in FIG. 4(b). As shownin FIG. 4(c), check valve 42 has an inlet 42b and an outlet 42d. Checkvalve 42 also has a flange 42e adapted to contact and be attached to thepackaging material layer 50. As described above, the packaging materiallayer 50 may comprise an insulator layer or include an outer insulatorlayer (not shown). Flange 42e may be attached to the packaging materiallayer 50 by tape with adhesives on both sides, or by a heat seal layercomposed of a material such as low-density polyethylene or Surlyn® brandresin from Dupont. After inlet 42b of the valve 42 is aligned with hole52, flange 42e is brought into contact with the packaging material layer50 so that the adhesive or tape attaches flange 42e to the packagingmaterial layer 50. If necessary, a fixture is used to apply pressurebetween flange 42e and the packaging material layer 50, and heat issupplied where necessary. Such fixture and heating operation is similarto those employed in bottle capping or sticker operations or fitmountsmounting operations. Instead of heating the valve in order to seal theflange 42e to the packaging material layer 50, ultrasonic energy may beapplied to the flange 42e to accomplish the same result.

After the valve 42 is thus incorporated into a portion of the protectiveenvelope, the protective envelope may then be employed to seal andenclose the battery cell 4 within a battery chamber.

FIG. 4(b) is a cross-sectional view of the battery assembly of thealternative embodiment of FIG. 4(a) showing the terminal connectedthrough a conductive portion of the check valve 42 to a laminar batterycell 4. The protective envelope 58 comprises packaging material layers50 and 56. The protective envelope 58 encloses the battery cell 4 withinthe battery chamber 16, where check valve 42 controls the passage offluids between chamber 16 and the environment outside envelope 58.

FIG. 4(e) is a cross-sectional view of battery assembly 40 of theembodiment of FIG. 4(a) and a vacuum chamber 70 used to evacuate thebattery chamber 16. A method for evacuation includes putting the batteryassembly 40 in a vacuum chamber 70, so that the pressure differentialbetween battery chamber 16 and the vacuum chamber 70 causes moisture,air and any other gases inside the battery chamber 16 to escape throughcheck valve 42 into the vacuum chamber 70, where they are drawn outthrough outlet 72 with a vacuum pump (not shown). After the batterychamber 16 has been evacuated, the battery assembly 40 is retrieved fromthe vacuum chamber 70, such that the atmospheric pressure causes theenvelope 58 to press inward on the battery cell 4. Check valve 42 onlypermits one-way movement of moisture and gas from the battery chamber 16to the environment, but does not permit entry of moisture, air or anyother gas from the environment to enter the battery chamber 16. Thelithium anode 4d in cell 4 is therefore securely isolated from moisture,air and other gases in the atmosphere.

Another method for evacuating the battery assembly is shown in FIG.4(f). FIG. 4(f) is a cross-sectional view of battery assembly of theembodiment of FIG. 4(a) and a vacuum hose 74 used to evacuate thebattery chamber 16. This method includes connecting the vacuum hose 74to the check valve 42, where the vacuum hose 74 is connected to a vacuumpump (not shown). In this manner, moisture, air and other gases inbattery chamber 16 are evacuated through the check valve 42.

In the above two evacuating methods corresponding to FIGS. 4(e) and4(f), the check valve 42 is caused by the atmospheric pressure to moveand contact the battery cell 4 such that the electrically conductiveportions of the check valve 42 will form an electrical contact withbattery cell 4.

Thus, the overall method for making the battery assembly in thisalternative embodiment is as follows. First, a one-way check valve 42 isconnected to a protective envelope 58. Then a laminar battery cell 4 andportions of the terminal 36 integral with or in electrical contact withthe cell 4 are held in a battery chamber 16 enclosed by the protectiveenvelope 58 by sealing the envelope around the battery cell 4 andportions of the terminal 36. The envelope 58 thus encloses a batterychamber 16 to protect the cell from the environment. Then, in the mannerdescribed above, the battery chamber 16 is evacuated.

From the above, it will be evident that the formation of the protectiveenvelope 58 and a sealed battery chamber 16 enclosing the battery cell 4may be performed under atmospheric pressure instead of under vacuumconditions. This renders a sealing operation much easier to perform.This is especially the case since the sealing operation must ensure thatthe protective envelope securely seals around the terminal 36 byapplying pressure and the heat thereto without breaking or otherwisedamaging the terminal 36.

Additionally, the one-way check valve 42 has safety benefits. Asdiscussed above, a defective battery may produce gases in the batterychamber 16. The one-way check valve 42 allows these gases to escape fromthe battery assembly 40 and prevents the battery assembly from burstingat the seal. When the internal pressure in the battery chamber isgreater than the atmospheric pressure, the one-way check valve 42 allowsgases to escape from the battery chamber 16.

As an additional precaution against the bursting of the batteryassembly, the terminal including the electrically conductive portions ofthe check valve 42 can allow for the terminal to lose contact with thebattery cell 4. FIG. 4(a) is a cross-sectional view of the batteryassembly of an alternative embodiment of the present invention showing aterminal including portions of the check valve 42 that have lost contactwith the laminar battery cell 4 due to the presence of gases in thebattery chamber 16. The packaging material layer 50 is adapted to flexoutward due to the presence of gases in the battery chamber 16. When thegases are produced by a defective battery, the terminal formed with thecheck valve 42 loses electrical contact with the battery cell 4. Whenthis occurs, the battery assembly 40 is disabled and the user is givenan indication that the battery is defective and should not be recharged.

The terminal also may be formed such that a portion of the terminal iscontained within the battery chamber 16.

FIG. 5 is a cross-sectional view of the battery assembly 60 of yetanother alternative embodiment of the present invention showing aterminal 62 of which a portion is contained within the battery chamber16. The terminal 62 has lost contact with the laminar battery cell 4 dueto the presence of gases in the battery chamber 16. A disadvantage offorming this type of terminal is the difficulty in properly sealing theterminal 62 to the packaging material layer 64 of the protectiveenvelope 66.

While the invention has been described by reference to variousembodiments, it will be understood that various modifications may bemade without departing from the scope of the invention, which is to belimited only by the appended claims.

What is claimed is:
 1. A method for making a battery assemblycomprising:providing a laminar battery cell and a protective envelopewith a terminal not in electrical contact with the cell; enclosing thelaminar battery cell in said protective envelope, said envelope defininga chamber; and evacuating and sealing said chamber causing the terminalto contact the battery cell.
 2. The method of claim 1, wherein saidproviding step comprises:providing a multi-layer package material withan electrically conductive middle layer, an outer insulator layer, andan inner insulator layer; forming said at least one terminal bystripping away portions of said outer and inner insulator layer; andforming said protective envelope from said multi-layer package material.3. The method of claim 2, wherein the protective envelope forming stepincludes sealing together pieces of said multi-layer package material,each piece of said multi-layer package material having a terminaltherein.
 4. The method of claim 1, wherein said providing stepcomprises:providing a layer of package material; forming said at leastone terminal by cutting away a section of the layer of packagingmaterial to form a hole and attaching an electrically conductiveterminal to cover said hole; and forming said protective envelope fromsaid layer of package material.
 5. The method of claim 1, wherein saidevacuating and sealing step comprises:sealing the protective envelope;and then, evacuating the chamber through a check valve on saidprotective envelope.
 6. The method of claim 1, wherein said evacuatingand sealing step comprises vacuum sealing the battery cell in theprotective envelope.